Statistics of radioactive decay

[jdou86]

Homework Statement

GRE

Relevant Equations

GRE PHysics

 

[mfb]

Same as in the other thread, you'll have to show what you did so far.
I extended the title to be more descriptive of the problem statement.

If you have a measurement, e.g. 100 counts in 7 seconds, what will your uncertainty on the rate be?

 

[jdou86]

10 since since sigma is sqrt of N so I set sqrtN/N=0.1 but that didn't get me very far

 

[Vanadium 50]

but that didn't get me very far

These problems take longer than a second to solve. Why don't you write down your strategy for solving this. In words.

 

[mfb]

10 since since sigma is sqrt of N so I set sqrtN/N=0.1 but that didn't get me very far

Well, that is an important step already. An uncertainty of 10 is an uncertainty of 10% here. Too much, you'll need more counts to get to 1%...

 

[jdou86]

These problems take longer than a second to solve. Why don't you write down your strategy for solving this. In words.

I'm good thanks

 

[jdou86]

Well, that is an important step already. An uncertainty of 10 is an uncertainty of 10% here. Too much, you'll need more counts to get to 1%...

Sorry it's supposed to be 0.01 but it still won't make sense because 10,000 counts represents 1000s measurement.

 

[jdou86]

Sorry it's supposed to be 0.01 but it still won't make sense because 10,000 counts represents 1000s measurement.

My desperate attempt whcih matches the answer

 

[mfb]

10000 counts is correct. You can use the existing measurements to get a rough estimate of the decay rate and use that to get the time you need to accumulate 10000 counts.